Purpose: 1- To evaluate accuracy of optic nerve sheath diameter (ONSD) measurements obtained by magnetic resonance imaging (MRI) in patients with craniosynostosis (CS) for detection of high intracranial pressure (ICP). 2- To correlate MRI derived ONSD measurements with those obtained by computed tomography (CT) scans in CS patients.
Methods: A retrospective review was conducted on CS patients who had MRI and age matched controls with normal MRI. Diagnosis of intracranial hypertension was based on presence of papilledema, direct ICP monitoring and/or lumbar puncture. The search also included patients with MRI and CT done within 30 days apart. ONSDs were measured 3 mm behind the globe on both modalities.
Results: Fifty-six CS patients (mean age 3.8 ±3.47 years) and 49 controls (mean age 3.7 ±3.62 years). Mean ONSD in patients with high ICP was significantly higher than in patients without high ICP (P=0.0001) and in controls (P<0.0001). The optimal ONSD threshold for predicting raised ICP in patients >1-year old was 6 mm (71.4% sensitivity, 89.7% specificity). Nineteen patients with 38 single eye MRI/CT pairs were identified. Substantial agreement between both modalities resulted (r=0.959, 95% CI:0.923-0.978), with 95% of measurements fell within limits of agreement (1.96 SD; ±0.6mm).
Conclusion: In CS patients, MRI derived ONSD measurements represent indirect non-invasive means of ICP assessment. Both MRI and CT measurements of ONSD gave comparable results, and as CT is frequently used in craniosynostosis as a diagnostic confirming and preoperative planning tool, ONSD measured by CT may give some idea about ICP in these patients.